1. Field of the Invention
The invention relates to a plant for producing power from solid fossil fuels, more particularly bituminous coal, made up of at least one boiler, in which the solid fuels are burned, the plant furthermore having a steam turbine and a gas turbine for producing power from the gas, the gases being cleaned of dust and sulfur in the plant before going into the gas turbine.
2. The Prior Art
In an earlier suggestion for such a plant (see the German Offenlegungsschrift No. 2,650,491), a fuel after grinding is fed to a boiler with a pressure firing system. The stack gases from the boiler are cleaned of dust and undesired, damaging substances, and furthermore undergo desulfurizing before being used in the gas turbine. The teaching of this earlier suggestion is that of designing a plant of this sort such that losses and troublesome conditions on operation are decreased. A further purpose was that of designing such a plant that it may be used in peak load power stations. The losses take the form of unburned material in the ash and the heat losses in the quenching water, while troublesome conditions on operation are caused, more particularly, by the tar-dust mix produced.
It will be seen that with the teaching of this earlier suggestion the part-burning or part-combustion and the later-stage burning take place in a single part of the plant, so that only one operation has to be automatically controlled. The operation may be so controlled as is necessary for a peak load power station; that is to say the power may be increased at a generally high rate, and decreased again to be in line with the power output of the plant without this being responsible for heat losses or its being necessary to make use of oil or further, other fuels in addition for supporting the burning process. Because burning of the fuel takes place in a boiler, the forming of tar is stopped and special parts of such plant, so far necessary in other designs, are not needed and troublesome conditions may be put to an end. On the stack gas side the pressure in the boiler is of the order of 10 bar, this generally being in line with the pressure relation or ratio of the turbine.
The main purposes effected by such a plant is that the amount of unburned material in the boiler ash becomes unimportant. The thermal efficiency is very much greater, because losses caused by evaporation of quenching water outside the steam circuit are generally put to an end, such losses having been so far necessarily produced in the case of gasification of the fuel. Because, furthermore, the fuel is burned in an apparatus itself under pressure, it is possible to do without a number of further units, used in past gasification systems, that is to say, more specially, a gas producer, while the system is better than a fluidized bed system because a very much smaller unit is needed for the burning process.